This invention relates to a method and apparatus for mechanically classifying rolling bodies according to the degree of irregularity they exhibit. The invention has particular, but not necessarily exclusive, application to generally cylindrically-shaped pellets for use in the fuel, breeder material or control rods of nuclear reactors.
In for example the manufacture of ceramic nuclear fuel elements, the uranium and/or plutonium dioxide is formed into generally cylindrically-shaped pellets which are comparatively fragile and are prone to damage such as chipping. Defects such as chips, cracks and other irregularities lead to non-uniform heat output or conduction which is undesirable. When the defect is in the form of a chip in the pellet surface the major dimensions of the pellet (length and diameter) are largely unaffected and, apart from laborious and time-consuming visual inspection with the consequent contamination risks to the operator, the only solutions offered hitherto for distinguishing pellets with damage of this nature have tended to involve expensive optical recognition of some kind.